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Is it possible to drain a carb dry under acceleration?

Did you crawl under the rear axle and see what that rubber fuel hose is doing in between sending unit and hard line?
 
I think the problem is that you are not running out of fuel, but running out of air. A 440, according to some of the formulas I've ran across, needs about 800 cfm at 6000 rpm of air flow. While the 650 carb may be jetted like an 800 carb, it can't pull enough air in on top end.

Since air flow may be limited, that may be causing enough vacuum to pull more fuel out of the carb than would be normal.

What size air filter is on the carb? Again, if that's not big enough, that can inhibit air flow as well, and with a small carb, that would not be good.

I may be wrong, but I think if you replace the carb, you'll take care of your problem.
 
Again, not to sound like an A-Hole, but have you checked it. With the issues you are having, something is not working as it suppose too.. Just because a part is new or says vented, does not mean it is or is operating the way it should..

What, the gas cap? I don't suppose I've ever seen that testing device before....
Funny you should mention it, though.
When I got it in my hands at NAPA, I was sitting there shooting the breeze with the guys and I actually pulled the cap out of the box and was playing with it.
I then placed it in my lips and blew threw it. :)
They got a kick out of that, although none were shocked I did it.
"Crazy Mopar Ed..."

Besides, you know these things have vented tanks, right?
Two vent lines, one of which goes all the way up into the trunk - and yes, that's all there, tested and functional as well.
There's damn near a breeze going through my tank.:D
 
I think the problem is that you are not running out of fuel, but running out of air. A 440, according to some of the formulas I've ran across, needs about 800 cfm at 6000 rpm of air flow. While the 650 carb may be jetted like an 800 carb, it can't pull enough air in on top end.

Since air flow may be limited, that may be causing enough vacuum to pull more fuel out of the carb than would be normal.

What size air filter is on the carb? Again, if that's not big enough, that can inhibit air flow as well, and with a small carb, that would not be good.

I may be wrong, but I think if you replace the carb, you'll take care of your problem.
The formula you're referring to:
http://www.carburetion.com/calc.asp
Says 649cfm for a "stock" motor; 725cfm for a "mildly built" one @ 6000rpm.

In other words, I agree with you. I had a Holley 3310 750cfm on it before the Eddy, but for the first time ever I had problems with that carb and wound up selling it.
I will be replacing this one with the 800cfm Edelbrock Thunder AVS before the year is out.

BTW, you can probably see from the bazillion pics I've posted on this site that it has the factory unsilenced air cleaner on it (with a fresh filter, of course).
Probably not the issue; they flowed better than the usual "closed" air cleaners.

By the way, the last few weekends I've had it out (and it's gotten some miles on the top end rebuild), it hasn't duplicated the failure yet. Knock wood.
Honestly, I keep waiting on the poor thing to toss a rod. :)

Thanks for the suggestions!
 
Did you crawl under the rear axle and see what that rubber fuel hose is doing in between sending unit and hard line?
You must have missed my posts previously, wherein I've stated that hose has been replaced and it has been purposely run short and perfectly straight between new fuel line and new sending unit.
All new.
All straight.
 
No, I saw the post. But I thought mine was fine too until I crawled under there. But yours is probably fine.

You must have missed my posts previously, wherein I've stated that hose has been replaced and it has been purposely run short and perfectly straight between new fuel line and new sending unit.
All new.
All straight.
 
You're carb is plenty big for the job. If it wasn't it would fall off EVERY time it reached a specific RPM under a load (as others have said ).

You cant accurately prescribe a CFM needs unless volumetric efficiency is calculated. Looking at your build that includes a stock intake (which is probably in the 80% volumetric efficiency range) We'll give it 85% to be conservative...

http://www.edelbrock.com/automotive/misc/tech-center/tech-discussion.shtml#dvecfm


(That intake is your biggest bottleneck in terms of delivering A/F to the bores as it has low volumetric efficiency)

***heres the math (*formula from Edelbrock's site)
A measure of air flow into and out of an engine (CFM = CID x RPM x VE ÷ 3456).
Example: What CFM is consumed by a 355 CID engine at 4500 RPM if VE = 105% (1.05)?
CFM = 355 x 4500 x 1.05 ÷ 3456
CFM = 485
Example: What CFM by the same engine at 6400 RPM if VE has fallen to 95% (0.9)?
CFM = 355 x 6400 x 0.95 ÷ 3456


So lets do the exercise on your setup. 440CID x 5800RPMS x .85VE of stock manifold / 3456= 627CFM
Now we know in real world conditions @ 5800 rpm's you engine cannot move more than ~627 cfm through the fuel delivery system due to the VE of your setup.
Now would it benefit from a bigger carb? maybe so. Especially at top end but that combo should do just fine with the current carb.

Can you doctor up a remote fuel supply with an electric pump to totally eliminate your current fuel lines?

Maybe borrow a carb to verify there isn't something wrong with yours?

Just trying to help, i know it can be frustrating .
 
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No, I saw the post. But I thought mine was fine too until I crawled under there. But yours is probably fine.
Thanks, but I've been under/over/in that damn thing a BUNCH here lately.
Repeatedly.
Keep trying to find what I've missed.
To top it all off, the car has behaved itself the last couple weekends since it happened.
Self-curing?
Reckon it's a good thing I don't plan to race it. :)
 
So lets do the exercise on your setup. 440CID x 5800RPMS x .85VE of stock manifold / 3456= 627CFM
Now we know in real world conditions @ 5800 rpm's you engine cannot move more than ~627 cfm through the fuel delivery system due to the VE of your setup.
Now would it benefit from a bigger carb? maybe so. Especially at top end but that combo should do just fine with the current carb.

Can you doctor up a remote fuel supply with an electric pump to totally eliminate your current fuel lines?

Maybe borrow a carb to verify there isn't something wrong with yours?

Just trying to help, i know it can be frustrating .
Yeah, the old carb formula told me a 650 would be adequate for street use on a mostly stock motor, so I went that route when I got rid of the Holley 3310 and went with the Edelbrock to begin with.
I have been rewarded, once I fiddled with the jetting and such a bunch, with VERY crisp and instant throttle response off idle @ low RPMs - the sucker snaps to just like a well-tuned Holley usually does, or even fuel injected cars do.

I had the (new) Holley 3310 on there before (750cfm vac sec), simply because I've had a LOT of luck with that exact carb on stock 440's in the past - they're usually an out of the box ready to rock sort of deal on them. Set it and forget it.
Usually.
Not this time, though.
Sold the Holley and bought the Edelbrock AVS 650cfm. A learning curve on those for sure, but they're damn near exact replicas of the original Carters, so I eventually remembered how to tune them and bought the kit to do so with.
The jetting in the carb right now is pretty much spot on what the Carters were back then, which just happens to be damn close to what the 800 AVS comes with, too.
Made me feel even more confident that it would be in the ballpark - and it is.

Having gone all over this thing over and over:
-zero leaks
-zero fuel fumes
-6.5psi fuel pressure at idle, so the Carter "hemi" pump is doing its' thing
(drops to a tad under 5 at WOT)

I typically drive the car every Saturday and every time, it has to regain its' prime (acts like no gas is left in the carb, so I crank it over about 5 seconds and let the pump fill 'er up again).
Once fuel gets up to the carb, she pops right off and after about 15 seconds of my goosing her and clearing her throat, she'll sit there and hold idle by herself - cold - with no choke.
(Always a good sign to me, anyways).
Yes, the heat crossover is blocked by the new Mopar/FelPro intake bathtub.

Problem only occurs when I'm full boogy floored, grabbing gears at 5500 or so. About time to get 3rd, face plant occurs.
I'm actually thinking this is something oddball, like the fuel is being thrown to the very rear of the tank and the new repro (probably junk) pickup literally can't get to it.
Grasping at straws, I am.
Speak like Yoda, I do.
 
Interesting development...
Had it out yesterday and when I hit the four lane and started tromping on it, it did the 3rd gear fall down bit again.
This time, however, I didn't lift all the way off the throttle. Instead, I lifted off full mash just a little, pumped it a couple times back to floored again and she caught her breath and started pulling again once I had it mashed hard enough to get into the secondaries.
It acted almost like the accelerator pump got fuel flowing through the thing again?
Most peculiar, mama. Woah.
 
Time to "shelve" all that carbuerator "BS" and move on to TB fuel injection. Let's face it, in the long run, at the rate your spending time and money on carbs, you could have installed TB twice over. Then again, maybe your issue isn't the carb at all. If it is, all I can say is, jets, floats, chokes, idle adjusting screws and all the other **** that comes with carbs, fu*k that! I wanna start it and go!
 
Time to "shelve" all that carbuerator "BS" and move on to TB fuel injection. Let's face it, in the long run, at the rate your spending time and money on carbs, you could have installed TB twice over. Then again, maybe your issue isn't the carb at all. If it is, all I can say is, jets, floats, chokes, idle adjusting screws and all the other **** that comes with carbs, fu*k that! I wanna start it and go!
I'm all for that, except for the cost.
BTW, this is still the same carb - has been for a while now.
 
moparedtn-- Almost has to be fuel delivery; think about it, if you're mashed on the throttle the acc. pump is bottomed out, no fuel below it and if you lift throttle it still takes a little bit to fill up that bowl up again. When you get it figured out we are all gonna kick ourselves for not figuring it out!!!
 
moparedtn-- Almost has to be fuel delivery; think about it, if you're mashed on the throttle the acc. pump is bottomed out, no fuel below it and if you lift throttle it still takes a little bit to fill up that bowl up again. When you get it figured out we are all gonna kick ourselves for not figuring it out!!!
Yeah and the only part in the chain at this point I haven't changed AGAIN is the fuel filter.
It may be new and all, but it's the only thing I haven't messed with twice.
I'll pull it out and temporarily replace it with a piece of tubing and see what happens.

Of course, a bigger carb is the eventuality here - in this case, I'm pretty set on the bigger version of the Edelbrock AVS (800 cfm I think?).
 
Different
Has this issue been resolved ? Old thread
Read my posts - Click on link
Thanx Scott - Bee 1971
https://board.moparts.org/ubbthread...8896/measuring-fuel-pressure.html#Post2658896
Lots of things have changed since then, honestly - not the least of which is the engine itself. :)
The "new" 440 I installed in May 2017 is fairly similar to the old one, though - although it does seem to have a bit more *** to it, it's still a warmed over 1972 unit with forged internals and the Mopar 484 purpleshaft cam.
A raggedly "reman" Edelbrock 750 sits on it now that I had to rework to get it working properly - I still need to replace that with a new one for sure.

To answer your question, the car sometimes still will falter in 3rd gear after beating on it all the way from a stop (4 speed), way up in RPM's - it literally falls flat on its' face when it happens, to the point of all but shutting off. I lift off of it, it catches its' breath and we go on like nothing happened.
Definitely a fuel starvation problem at the point it happens - and here's a kicker to the whole thing:
It not only seems to be sensitive to temperature, but to what gas I bought, too.
Ethanol-free stuff does it less. Less than a 90 degree day does it less.
That sort of thing.

My conclusions are many - I have a Howards fuel pump pushrod to install; I want the 800cfm Edelbrock AVS carb for it; and the repro sending unit needs the hell out of there, too.

Oh, P.S.: Sometimes it doesn't do it at all, too. :)
 
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I hear you on the inconsistency

It’s supposed to bee nice and cool this weekend here in WI

Will bee interesting seeing how the car responds

Only thing I have not done is drop the fuel tank recently - Was replaced brand new probably ten years ago

All vent hoses are brand new - Fuel filter and hoses new

Sending unit is factory 1971 and

I might open the carb and re adjust the float levels

Edelbrock also sells a .110 needle and seat

I run 93 octane with 10% Ethanol here in Green Bay
Very few stations selling 93 octane

Thanx for responding back
 
I suspect a restriction in the reproduction sending unit (sock?) since the entire rest of the fuel line
(all 3/8") has been replaced with new and it's all metal (repop Fine Lines stuff) except for the small
pieces at tank and fuel pump (3/8" "ethanol resistant" rubber stuff).
I'll install the Howard's pushrod just because I have it and it's new.
The fuel pump is the new production "hemi" Carter unit.
The carb will get replaced just because it came with the engine and I had to go through it (including
getting the jets and rods changed out to what it's supposed to come with - "reman" my ***!).
It has a few goofy spots in its' behavior, too. A new one clears a lot of that up.

These things are never "done", after all. :)
Good luck to you with yours!
 
Different

Lots of things have changed since then, honestly - not the least of which is the engine itself. :)
The "new" 440 I installed in May 2017 is fairly similar to the old one, though - although it does seem to have a bit more *** to it, it's still a warmed over 1972 unit with forged internals and the Mopar 484 purpleshaft cam.
A raggedly "reman" Edelbrock 750 sits on it now that I had to rework to get it working properly - I still need to replace that with a new one for sure.

To answer your question, the car sometimes still will falter in 3rd gear after beating on it all the way from a stop (4 speed), way up in RPM's - it literally falls flat on its' face when it happens, to the point of all but shutting off. I lift off of it, it catches its' breath and we go on like nothing happened.
Definitely a fuel starvation problem at the point it happens - and here's a kicker to the whole thing:
It not only seems to be sensitive to temperature, but to what gas I bought, too.
Ethanol-free stuff does it less. Less than a 90 degree day does it less.
That sort of thing.

My conclusions are many - I have a Howards fuel pump pushrod to install; I want the 800cfm Edelbrock AVS carb for it; and the repro sending unit needs the hell out of there, too.

Oh, P.S.: Sometimes it doesn't do it at all, too. :)

Ed, I had the same issue on mine. In AZ during the day it would hit a wall and stumble when getting on it. At night, cooler temps I could jump on it and no stumbles at all. I was running an Eddy 800 cm avs, 3/8" fuel line, Edelbrock high volume mechanical pump.

I hooked up a fuel gauge and mounted it up on the windshield. Pressure was 6.5psi. During the day, wot, the pressure would drop to zero and a few seconds later it would stumble. At night, wot, the pressure only dropped to 2ish psi. Just enough to keep up.

Sent the junk Eddy pump back to Summit and ordered a Holley electric pump and no issues ever again. I have since installed a Holley Sniper tank and in-tank pump. Quieter and still gives it plenty of fuel.
 
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